1. Field of the Invention
The invention relates to a switch, more particularly to a tilt switch that accurately undergoes on/off operations.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional tilt switch 1 includes an insulated casing 10, a ball member 16, infrared light emitter and receiver 17, 18, and an insulated top cover 19.
The insulated casing 10 has two spaced-apart receiving spaces 11 extending from a stepped-shaped top face 101 to a bottom face 102, two pairs of through holes 12 formed in the bottom face 102 and each pair communicating with the corresponding receiving space 11, a groove 13 extending downwardly from the top face 101 and defined by an upper peripheral wall 131 and a tapered lower peripheral wall 132, and two notches 14 each formed between the groove 13 and the corresponding receiving space 11. Each notch 14 converges from the corresponding receiving space 11 toward the groove 13, and communicates with the groove 13 through a vertically extending slot 141 formed between the groove 13 and the corresponding notch 14.
The ball member 16 is disposed in the groove 13, and may be made of a copper or iron alloy, or may be gold plated.
The infrared light emitter 17 has a main body 171, two contact terminals 172 extending downwardly from the main body 171, and an emitter head 173 projecting on one side of the main body 171. The emitter 17 is inserted into one of the receiving spaces 11 with the emitter head 173 extending into the corresponding notch 14 and the contact terminals 172 extending out of the bottom face 102 of the casing 10 via the corresponding through holes 12.
The receiver 18 is used to receive a light signal emitted by the emitter 17, and has a main body 181, two contact terminals 182 extending downwardly from the main body 181, and a receiver head 183 located on one side of the main body 181. The receiver 18 is inserted into the other one of the receiving spaces 11 with the receiver head 183 extending into the corresponding notch 14 and facing the emitter head 173. The receiver head 183 and the emitter head 173 cooperatively form a light path (R). The contact terminals 182 extend out of the bottom face 102 of the casing 10 via the corresponding through holes 12.
The insulated top cover 19 is mounted on the top face 101 of the casing 10, and is connected to the casing 10 through a high frequency sealing technique.
When the tilt switch 1 is mounted upright on a circuit board (P) and is disposed in an untilted state, the ball member 16 falls into the lower peripheral wall 132 by virtue of gravity, and blocks the light path (R) so that the tilt switch 1 is in an “OFF” state. When an external force is applied to the tilt switch 1 so as to incline the tilt switch 1, the ball member 16 rolls away from the lower peripheral wall 132 and out of the light path (R), thereby shifting the tilt switch 1 to an “ON” state.
Although the conventional tilt switch 1 can achieve its intended purpose, because the slots 141 formed between the groove 13 and the corresponding notches 14 are elongated, light scattering from the emitter 17 and incident on an inner wall face of the top cover 19 may be reflected by the inner wall face of the top cover 19 toward the receiver 18. Therefore, it is possible for the receiver 18 to receive improper light signals from the emitter 17, even if the ball member 16 is in its blocking state.